The menisci are two C-shaped discs of fibrocartilage found between the condyles of the femur and the tibial plateau which play a critical role in the load transmission, load distribution, shock absorption, joint stability, and lubrication of the knee. Despite the recognized importance of the tissue, arthroscopic removal of a torn meniscus is one of the most common orthopedic procedures performed in the United States. Because the tissue has limited healing potential, the clinical outcomes of subtotal meniscectomies are generally poor. At this time, a reliable surgical procedure to replace significant loss of meniscal tissue does not exist. There is no autologous procedure to replace the meniscus and the results of allograft replacement are unreliable.
Another approach is that of tissue engineering. Current approaches include synthetic polymer scaffolds and collagen meniscus implants. With synthetic polymer scaffolds, polyurethane sponges are used to replace the meniscus. This approach has led to inconsistent results. Fibrocartilage growth is seen in some studies using this technology while in others fibrous tissue did not remodel into fibrocartilage. The underlying cartilage was protected in some studies but not protected in others.
Another type of meniscus implant uses a sponge containing collagen, hyaluronic acid and chondroitin sulfate. There is promising preliminary data for this implant, but it is not widely accepted by the orthopedic community because of issues with cytotoxic byproducts of cross-linking and scaffold shrinkage.
Both of these approaches generate an amorphous structure, the mechanical properties of which may not be appropriate for a device designed to replace the meniscus. Thus, while scaffold technology holds promise, no methods have met with the clinical success necessary for acceptance by the orthopedic community. There remains a need for a tissue engineered scaffold with the necessary mechanical properties and biocompatibility for treatment of significant meniscal damage.